1. Field of the Invention
The present invention relates to the storage of molds used to bend glass sheets by the gravity sag method in the fabrication of bent glass windshields and other bent glass articles.
2. Description of Technical Background and Patents of Interest
In the fabrication of laminated bent windshields for automobiles and the like, a tunnel-like bending lehr having a controlled heating pattern is used to heat glass sheets to their shaping temperature while supported on outline-type bending molds. The molds are loaded with a pair of glass sheets at a loading station near one end of the lehr, and move on a main conveyor through the hot lehr where the supported glass sheets are shaped by gravity sagging onto the shape of the outline type bending molds and then are removed from the molds at an unloading station near the exit end of the lehr.
An exit elevator is provided to transfer the empty molds and their support carriages from the vicinity of the unloading station to a return conveyor located immediately above the roof of the bending lehr. The latter extends the entire length of the lehr from an upper position defined by said exit elevator to an upper position defined by a loading station elevator near the entrance of the lehr. The loading station elevator lowers the mold and its support carriage into the vicinity of the loading station at the entrance end of the glass sheet bending lehr and at the beginning of the main lehr conveyor that transports the molds laden with glass sheets. The main lehr conveyor, the return conveyor and the exit and entrance elevators at the ends of the conveyors provide a cyclic conveyor system for moving glass sheet bending molds for a glass sheet bending operation.
Periodically, it becomes necessary to change the production of the glass sheet bending molds from one pattern to another. In the past, this change has required the removal of the molds that were no longer needed to a storage area remote from the bending lehr and the retrieval from said remote storage area to the vicinity of the bending lehr of a new set of bending molds adapted to shape glass sheets into the shape desired for a new pattern. The difficulty of maintaining and transferring molds under such circumstances has been accepted reluctantly in the past. However, the present invention has improved the efficiency of storing and replacing bending molds whenever a pattern change is indicated.
Typical prior art patents showing the mold cycling system of the prior art include U.S. Pat. No. 3,216,811 to James S. Golightly and U.S. Pat. No. 4,072,492 to William A. Castine, Jr. These prior art cycling systems were used with mold storage areas remote from the lehr.